void PreviousButtonClicked(object sender, EventArgs e)
{
if (op1.Checked)
{
tl.CalculateUserMarks(1);
}
else if (op2.Checked)
{
tl.CalculateUserMarks(2);
}
else if (op3.Checked)
{
tl.CalculateUserMarks(3);
}
else if (op4.Checked)
{
tl.CalculateUserMarks(4);
}
Question question = tl.GetPreviousQuestion();
if (question != null)
{
DisplayQuestion(question);
}
}